The present invention relates to a current sensor for measuring direct and alternating currents, and more particularly to a current sensor operating by compensating a magnetic field introduced by the current.
Current sensors of this type are known in the art as compensation current transformers and measure direct and alternating currents by compensating the magnetic field generated in a magnet core by the measuring current with a compensation current in a secondary winding. The magnetic circuit includes a sensor, typically a magnetic field probe, that controls the compensation current by detecting deviations from a zero magnetic field. The secondary current accurately mirrors the current to be measured, as described, for example, in DE 3718857 A1.
To reduce the power requirement for the compensation current and to reduce losses, DE 19642472 A1 discloses the use of a clocked switching amplifier which is driven by a pulsed drive signal. Such compensation current transformers are useful, for example, for precision measurements of the motor currents of high-precision servo drives. In particular, the motor will only run true if the misadjustment of the compensation current transformer is very small (offset <0.1% over the temperature range).
However, it has proven difficult to directly implement a conventional peak-type rectification of the probe signal in an integrated circuit.
It would therefore be desirable and advantageous to provide an improved current sensor which obviates prior art shortcomings and which is highly accurate and also less expensive than conventional current transformers. Furthermore, it would be desirable and advantageous to be able to integrate the electronic system and operate, at least for smaller currents, with a single-sided 5V supply.